The predominant type of domestic, private sewage disposal system is the septic tank and drainage field. Waste from the house flows into a water tight septic tank. There it remains approximately 24 hours while bacteria reduce many of the solids to a liquid state. At the end of this interval, the liquids flow out of the tank into a leaching field through a network of porous pipes. These porous pipes are placed fairly close to the ground surface, which allows air to get to the liquids and evaporate them before they have a chance to drain off into the ground water.
In many localities, the porosity of the ground is not sufficiently high to permit the sustained operation of a septic leaching field and it has been found that, in such areas, the use of two, separate leaching fields used alternately, will enable the ground in a first field to dry out while the second field is in use.
Prior to the advent of plastic sanitary pipe, sanitary leaching fields were connected to the septic tank by means of clay soil pipe. In those localities which required the use of two alternate leaching fields, a sanitary diversion valve was employed to selectively connect the first or the second leaching field to the septic tank. The prior art sanitary diversion valves were made of metal parts which tended to be unreliable due to their tendency to corrode under long term use. The clay soil pipe was sealed to the prior art sanitary diversion valve by packing oakum into the joint, followed by a coating of cement mortar.
In the early 1970's, two types of plastic pipe came into common use by the construction industry for sanitary pipe. The first is a tough, rigid thermoplastic, acroylonitrile-butadiene-styrene, known as ABS resin. ABS resins used in plastic sanitary pipe, are true graft polymers consisting of an elastomeric polybutadiene or rubber phase, grafted with styrene and acrylonitrile monomers for compatability, dispersed in a rigid styrene-acrylonitrile matrix. ABS plastic sanitary pipe has a high impact resistance, a high mechanical strength, and resistance to creep under load. This desirable combination of properties is retained over a temperature range of minus 40.degree. to 140.degree. Fahrenheit with little change. ABS resins exhibit resistance to chemical attack by water, aqueous salt solutions, alkalies, nonoxidizing inorganic acids, many food stuffs and household cleaners and oils. ABS plastic sanitary pipes may be joined by means of solvent welding using a solvent such as butanone. The other type of plastic which has come into wide use in the construction industry for sanitary pipe is polyvinyl chloride, otherwise known as PVC. PVC resins can be formed as rigid structural materials which have a high resistance to chemicals, solvents and water. PVC plastic sanitary pipe has a good resistance to weathering, is low in cost and has a good abrasion and impact resistance.
In adapting ABS and PVC plastic sanitary pipe to septic tank disposal systems employing two alternate leaching fields, problems have been experienced in securely joining the plastic sanitary pipe to the sanitary diversion valve so that a reliable, leakproof seal can be made therewith. The prior art techniques of employing oakum and cement mortar result in an unreliable seal. Still another problem which has been associated with prior art sanitary diversion valves, is that the valve core tends to leak through the housing at the point at which access is made and further that dirt and other debris from the ambient become lodged at the valve handle. The valve handle is also susceptible to tampering by unauthorized persons.